1. Field of the Invention
The present invention relates to a releasing sheet. More particularly it pertains to a releasing sheet which is non-silicone based, is favorable in releasability from a tacky adhesive agent layer, brings about excellent adhesiveness between a releasing agent layer and a substrate, and is suitably employed for the purposes of use concerning precision electronic-machinery/equipment.
2. Description of the Related Arts
In recent years, a tacky adhesive sheet has been employed in a variety of stages and systems for the production processes of precision electronic-machinery/equipment such as ceramic capacitors, hard disc drives and semiconductor equipment.
Since in the case of the above-mentioned tacky adhesive sheet which is used in production processes of precision electronic-machinery/equipment, there is a fear that a silicone based tacky adhesive gives rise to electronic part troubles due to silicone compounds having a low molecular weight contained in the aforesaid tacky adhesive, there are used in general, non-silicone based tacky adhesives, for instance, tacky adhesives of acrylic base, polyester base, polyurethane base and the like.
The tacky adhesive sheet is laminated with a releasing sheet comprising a substrate and a releasing agent layer located thereon for the purpose of protecting the tacky adhesive agent layer until the time of use.
A silicone based releasing agent is frequently used in the releasing agent layer for the releasing sheet so far as the general purposes of use are concerned.
However in the case where use is made of the silicone based releasing agent for the above-mentioned purposes of use, there is a fear that silicone compounds having a low molecular weight contained in the aforesaid releasing agent migrate to a tacky adhesive agent layer and resides therein, thereby causing electronic part troubles as is the case with the silicone based tacky adhesive.
Accordingly an attempt is made to employ an alkyd based resin which is known as a non-silicone based releasing agent {for instance, refer to Japanese Patent Application Laid-Open No. 49685/1982 (Showa 57)} or a long-chain alkyl based resin {for instance, refer to Japanese Patent Application Laid-Open No. 249757/2002 (Heleisei 14)}.
Nevertheless in the case of using any of the resins thus cited, there is brought about a problem in that the releasing power between a tacky adhesive agent layer and a releasing agent layer is too strong to peel off the layers from each other.